How to trigger an alarm in DSC module if after re-enabling alarming

[TomBrass]

Okay, the method was actually fully described by Thomas, so sorry for taking credit.  😉

[TomBrass]

I never got an answer to my question about handling Boolean alarms, and now the customer is asking about it again.  Pesky customers, wantings things to actually work. 😉  It is frustrating to me that disabling an alarm, then re-enabling it doesn't trigger the alarm again.  Maybe that works fine for some applications, but for our application, it really sucks.  The customer wants to disable the alarm temporarily to see if it will go back to normal on its own.  For example, say you are monitoring the temperature of a cooler.  If someone opens the door, it will go out of limits, but then if the door is closed again, it should return to normal.  The customer wants to know if it doesn't go back to normal.  We used the method described earlier in this thread, and that works great for analog signals, but those analog signals change all the time.  Thus, they are constantly updated.  A Boolean, on the other hand, will stay at True, so the value is never re-evaluated, and thus the alarm is never retriggered.  Is there a way to fool the system into thinking that the value changed?  Is there a way to force an update of the value?

BTW, I am using LabVIEW 8.6 and DSC 8.6.  If this issue has been fixed in a later version, I'd like to know that as well.

Thanks!

Tom Brass

Certified LabVIEW Architect

Saint Bernard Engineering, Inc.

www.saintbernardengineering.com

[ThHagel · Accepted solution]

Hi Tom,

I guess I found a solution that might work for any type of shared variable as long it is network bind:

I know this looks odd, but it works. The variable value gets re-evaluated after binding gets re-activated. URL must be stored and written back because it gets deleted as soon binding is deactivated. Give it a try....

BTW: I tried LabVIEW 2010 SP1 and we still get the same behavior as in 8.6 ( I'll try LabVIEW 2011 SP1 and let you know the result - have to install it first)

Regards,

Thomas

[TomBrass]

I'll give it a try.  Thanks!

Tom

[ThHagel]

Hi Tom,

wanted to let you know that Labview 2011 SP1 still reacts the same way (no re-evaluation after re-enabling alarms).

Regards,

Thomas

[TomBrass]

I tested out your solution today, and it works!  Thank you so much!!  I wish I could give you more than one kudos.

[NNS-CAO]

Thomas,

We have been using the suggested solution for several years now and it works well for individual channels. We have a system with about 100 shared variables and 13 of those channels have alarms that the user can enable/disable. We have tried to impement an "enable/disable all" feature for those 13 alarms and have found if you repeat that method multiple times it will occasionally cause the PSP engine to "reset". What I mean by "reset" is that the connection to all libraries and shared variables will be lost and will return after about 30-45 seconds. The labview program continues to run normally and eventually the system will recover. Have you seen this behavior before?

Thanks,

Chris Omweg

[ThHagel]

Hi Chris,

I do not use the DSC module anymore, since it was a very disappointing experience using it for larger projects. The 2011-version was the last one I used and I did not try newer ones (actually I was so pi***d that I cancelled my SSP). Nevertheless, I did not see this behavior before. But that doesn't mean a thing, since I don't know how newer versions behave.

So, I can only wish you good luck solving this! Sorry I can not help 😞

Thomas